Allow extensions to throw more fine-grained exceptions

This allows to tell the user something more helpful than
"File could not be saved" (leaving the reason open for speculation).

The former implementation somehow grew to only ever throw
Inkscape::Extension::Output::save_failed for any exception that
occurred (which did not really matter as we did not throw anything
else but certainly wasn't very useful either).

Questionable throwing behavior was introduced in commits trying to
workaround other issues:
- output.cpp a874b82b41c08fc1738b449d400fcc6aeb85d72a
- system.cpp d8d60c60ebeeefb068d9b68bf7d96f1f1f88518a

0 files changed, 0 insertions, 0 deletions